Balance bar having a reduced axial thermal stress resulting from high temperature manufacturing methods

Abstract

A manufacturing process that prevents stress between a titanium flow tube and a surrounding steel balance bar due to a brazing operation. A straight tube Coriolis flowmeter having a titanium flow tube is surrounded by a balance bar having separate longitudinal halves. The balance bar halves are connected to each other by an elongated side channel on each side of the balance bar halves. The elongated side channels are radially spaced apart from the balance bar halves but connected to the balance bar halves by means of tubular pegs which extend into holes in the side channels. The flow tube is joined by brazing via connecting rings to the balance bar halves and to an inner end of the pegs. The radially outer end of the pegs are inserted into the holes in the side channels and welded. Circular welds and slots in the side channels reduce axial shrinkage of the side channels as the welds cool. This prevents axial stress on the flow tube.

What is claimed:  
     
       1. A Coriolis flow meter adapted to be connected to a system having a material flow, said Coriolis flow meter having a balance bar and a flow tube adapted to be vibrated in a drive plane in phase opposition to generate Coriolis deflections of said vibrating flow tube with material flow; pickoff means that detect said Coriolis deflections to generate signals representing information pertaining to said material flow; said balance bar is coaxial with said flow tube and surrounds a portion of said flow tube, said Coriolis flow meter further comprises: 
       connecting rings;  
       separate halves of said balance bar each being coaxial with said flow tube and with each half having an axial outer end connected to a surface of said flow tube by one of said connecting rings;  
       elongated apparatus that interconnects the inner axial ends of said balance bar halves, said elongated apparatus is located on the neutral plane of the drive mode of said balance bar and is spaced apart from the outer radial surface of said balance bar halves;  
       said elongated apparatus and said balance bar halves vibrate in said drive plane as an integral structure.  
     
     
       2. The Coriolis flow meter of  claim 1  characterized in that said elongated apparatus comprises: 
       a plurality of elongated elements each spaced apart from the outer radial surface of said balance bar halves and oriented parallel to the longitudinal axis of said balance bar halves.  
     
     
       3. The Coriolis flow meter of  claim 2  characterized in that said elongated elements define side channels that are-u-shaped in a cross section perpendicular to their longitudinal axes. 
     
     
       4. The Coriolis flow meter of  claim 2  characterized in that said elongated elements define side channels that are non-U-shaped in cross section. 
     
     
       5. The Coriolis flow meter of  claim 2  having pegs connecting said elongated elements to said balance bar halves; 
       said pegs, said elongated elements and said balance bar halves vibrate in said drive mode as an integral element.  
     
     
       6. The Coriolis flow meter of  claim 5  having holes in said elongated elements and in said balance bar halves for fixably receiving said pegs. 
     
     
       7. The Coriolis flow meter of  claim 6  characterized in that said pegs are bonded at a first end to said holes in said balance bar halves and welded at a second end to said holes in said elongated elements. 
     
     
       8. The Coriolis flow meter of  claim 6  characterized in that said pegs are tubular with a hollow center core. 
     
     
       9. The Coriolis flow meter of  claim 6  characterized in that said pegs are circular in cross section. 
     
     
       10. The Coriolis flow meter of  claim 6  characterized in that said pegs have an non circular cross section. 
     
     
       11. The Coriolis flow meter of  claim 6  characterized in that there is at least one peg connecting each elongated element with each of said balance bar halves. 
     
     
       12. The Coriolis flow meter of  claim 6  characterized in that there are at least two pegs connecting each elongated element with each of said balance bar halves. 
     
     
       13. The Coriolis flow meter of  claim 6  characterized in that said pegs are tubular with each peg each having a first end bonded to one of said balance bar halves and a second end welded to one of said elongated elements. 
     
     
       14. The Coriolis flow meter of  claim 5  characterized in that said elongated elements have slots oriented transversely to a longitudinal axis of said elongated elements, said slots limit axial shrink of said elongated elements due to the welding of said pegs to said elongated elements. 
     
     
       15. The Coriolis flow meter of  claim 2  characterized in that said Coriolis flow meter has two elongated elements oriented longitudinally on opposite sides of said balance bar. 
     
     
       16. The Coriolis flow meter of  claim 13  characterized in that the geometry of said weld defines an endless closed loop. 
     
     
       17. The Coriolis flow meter of  claim 13  characterized in that the geometry of said weld defines a circular pattern.